Develop Reference

How to "refresh" a JFrame inside an actionperformed method?

I try to design a GUI for a neural network I made recently. I am using the MNIST-dataset and want to display the handwritten digit using JPanels with the brightness-values written inside. By pressing the "train"-button the network gets trained and every new digit is displayed. However this happens in a for loop in the actionperformed method of the button and it seems that I can´t change the background of the labels or the text(at least it doesn´t display the changes) until the last one. I don´t know whether I´m right but it seems that only the last change gets displayed. That´s why my question is whether it is possible to "refresh" the JFrame inside the actionperformed method.
I already have tried revalidate(), invalidate() & validate(), SwingUtilities.updateComponentTreeUI(frame), but none of them worked.
Here is the relevant part of my code:
train.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
for (int i = 0; i < iMax; i++) {
...
digitRefresh(reader.getInputs()[i], (int) reader.getInputs()[i][0], 0);
}
}
});
.
public void digitRefresh(double[] pixelValue, int target, int result) {
for (int i = 0; i < 784; i++) {
double value = pixelValue[i + 1];
int brightness = (int) (value * 255);
l_digit[i].setText(String.valueOf(value));
l_digit[i].setBackground(new Color(brightness, brightness, brightness));
}
l_target.setText(String.valueOf(target));
l_result.setText(String.valueOf(result));
this.revalidate();
}
thank you for every awnser and sorry for my bad english.

The simplest thing to do is start a new thread.
#Override
public void actionPerformed(ActionEvent e) {
new Thread( ()->{
for (int i = 0; i < iMax; i++) {
...
final int fi = i;
EventQueue.invokeLater( ()->{
digitRefresh(reader.getInputs()[fi], (int) reader.getInputs()[fi][0], 0);
});
}).start();
}
Now all of the work is being done on a separate thread, then as the ... work finishes, digit refresh method called from the EDT. Notice the final int fi part. There are caveats about going back and forth on threads so it is good to look into better controls than just using thread.
Swing worker for example:
How do I use SwingWorker in Java?

Changing the delay of the timer without creating a new one every time the method runs

So basically I have a timer method in my program which uses the integer z as it's parameter as well as the delay for the timer itself. But every time I run this method, it creates a new timer not deleting the old one. So I decided to add an if else block that made it so that it only created a timer on the first time but now it's saying that it might not have been initialized because it was initialized in the if else block. Can someone help me?
public void timer(int z) {
int count = 0;
Timer tester;
z = (60000 / z);
decide = true;
ActionListener taskPerformer = new ActionListener() {
public void actionPerformed(ActionEvent evt) {noteDecider();}
};
if(count == 0) {
tester = new Timer(z, taskPerformer);
tester.start();
}
else {
tester.setDelay(z);
tester.start();
}
count++;
}

I would say that if you are concern about optimizing your code you should look into optimizing your Timer class. Like moving the ActionListener object inside Timer itself and more. All your timer(int z) method is doing is trying to use an object to keep track time not managing the lifecycle of Timer objects.

Make a timer in swing

For this game I'm making for java class, I want a timer display in the corner that counts up from 0
I made a variable that represents seconds, which ==> double s =0;
My idea was that using a Timer object where I could increment the variable every second and use the repaint() method on the string
However, I misinterpreted how the timer object works, and after the delay it counts up rapidly to infinity. I have no idea what to do now. A hint would be appreciated.
Here is my code,thanks for any help:
int delay = 5000; //milliseconds
ActionListener taskPerformer = new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
s=(int)s+1;
}
};
new Timer(delay, taskPerformer).start();
String t = "" + s;
g.drawString(t, 100, 100);
repaint();

How about something like this: (you might have to change it for your needs)
boolean temp=true;
long startTime = System.nanoTime();
while(temp){
float time = (System.nanoTime()-startTime)/ 10000000.000f;
System.out.println(time);
}

What you can try doing is implementing the Runnable interface and then starting a new Thread of the class that you are using to draw your Components. Since Thread implements the Runnable interface, you will be able to create a new point of execution in the program where you can call a delay with Thread.sleep() before repainting your components. Here is an example of what you should try doing:
Thread thread = new Thread(ClassNameHere);
thread.start();
If you are interested in trying this out, more information can be found on the API on Threads and on the Runnable interface.

Display delayed text on User's screen

Hello!
I am trying to display a text on the Screen (with Java), but I want it to be delayed, like, every 0.1 seconds, a letter of the text would appear on the screen. It's like Pokemons dialogs. Here's what I am talking about: https://www.youtube.com/watch?v=yUS1IcC5CBY
I don't want the fade and the acceleration of the text, I just want the text to appear letter-by-letter. Also, I would like the text to be a String. Please, can you help me?
Thanks a lot in advance!

You can use two methods:
One is Thread.sleep(), which is shown above:
private static String message = "Your Message";
private static JLable label = new JLabel();
private static String labelMessage = "";
for(int i = 0; i < message.length(); i++){
labelMessage += Character.toString(message.charAt(i));
label.setText(labelMessage);
try{
Thread.sleep(howManyMillisecondsYouShouldWait);//if you want to do it every .1
//seconds, just wait 100 milliseconds.
}catch(InterruptedException e){
Thread.currentThread().interrupt();
}
}
that will forever print it to the screen every 100 milliseconds. However, the only trouble with using Thread.sleep is (and I somehow just learned this the other day, even though I've been programming for a long while) it is not always accurate. It may sleep 100 ms, it may sleep 150, etc. Secondly, a slower computer may take longer to sleep through it.
The other method which you will use more often (probably) is to check the actual time of your system and see if it's been long enough since you last printed it to the screen, like this:
private static long timeOfLastWrite;//at what time did you last update the text?
private static long deltaTimeSinceLastWrite;//how long has it been since you last updated the text?
private static long timeOfFirstWrite;//when did you start?
private static long deltaTimeSinceFirstWrite;//how long has it been since you started?
private static String message = "Your Message";
private static JLabel label = new JLabel();
private static String labelMessage = "";
//print once here:
timeOfFirstWrite = System.currentTimeMillis();
timeOfLastWrite = System.currentTimeMillis();//every time you print to the screen, make
//sure that you make note of it by setting the timeOfLastWrite variable equal to the current time.
labelMessage += Character.toString(message.chatAt(0));
while(!labelMessage.equals(message)){
deltaTimeSinceLastWrite = System.currentTimeMillis() - timeOfLastWrite;
if(deltaTimeSinceLastWrite >= 100){
timeOfLastWrite = System.currentTimeMillis();
deltaTimeSinceFirstWrite = System.currentTimeMillis() - timeOfFirstWrite;
int currentIndexOfChain = (int) deltaTimeSinceFirstWrite / 100;
if(currentIndexOfChain >= message.length()){
currentIndexOfChain = message.length() - 1;
}
labelMessage = message.substring(0, currentIndexOfChain + 1);
label.setText(labelMessage);
}
}
This method isn't even slightly necessary for a program so simple as writing text to the screen 10 times a second. However, it's good to get into the practice of it. You'll learn that if you create a character and tell him to move 10 pixels, Thread.sleep(100), and move again and etc... that on a slower computer, the character will move slower. However, if you tell it to wait until a certain amount of time has passed according to your computer's time, if the user lags out and it takes 200 milliseconds before it tells the character to move again, you can account for that by simply making him move twice as far -- I think it's called framerate independence.
If I did anything wrong with the delta time management please let me now. Again, I just learned about this the other day even though I've been programming for awhile, so don't worry about it too much if you're just now learning to program.
And that's how you make an incredibly long (possibly too long) answer to an incredibly simple question. I hope you benefit from this response.

I'm unable to use Thread.sleep(x) or wait(): java.lang.InterruptedException; must be caught or declared to be thrown
try {
Thread.sleep(100);
} catch(InterruptedException ex) {
Thread.currentThread().interrupt();
}

You may use this code for doing so. Simply put a thread to print the text onto a jLabel.
new Thread(new Runnable() {
#Override
public void run() {
String x="";
String txt="Hello this is a sample text. Let us see how this works.";
for(int i=0;i<txt.length();i++){
try {
jLabel1.setText(x=x+txt.charAt(i));
Thread.sleep(100);
} catch(InterruptedException ex) {
Thread.currentThread().interrupt();
}
}
}
}).start();

How about this?
import javax.swing.Timer;
import java.awt.event.*;
import javax.swing.JFrame;
import javax.swing.JLabel;
public class DelayText
{
public String example = "As you can see, this sentence is being printed out a character at a time.";
public String transfer = "";
public Timer t;
public int i = 0;
public JFrame f;
public JLabel l;
public DelayText()
{
f = new JFrame("Example");
l = new JLabel();
f.add(l);
f.setSize(450, 200);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setVisible(true);
TimerListener tl = new TimerListener();
t = new Timer(100, tl);
t.start();
}
public static void main(String[] args)
{
DelayText d = new DelayText();
}
private class TimerListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
if(i < example.length())
{
transfer += (example.charAt(i));
l.setText(transfer);
i++;
}
if(i >= example.length())
{
t.stop();
}
}
}
}
I am using the timer to create a delay between each character outputted on the JFrame. I noticed a lot of these other ones were a bit more complex, thought this might make things a bit easier to understand.

Code works sometime but not others (memory or thread issue)

I am having this odd issue, and I am not sure what is causing it. Some times the issue isn't even there. From what I am guessing, is that this is a Java memory issue or some sort of threading issue.
I have a Ship and the ship shoots Bullets If I hold down the Space key the ship shoots the bullets. I have the bullets set to fire off every 200 milliseconds. Some times they shoot fine and move at the same speed! Other times, they shoot they move at different speeds. What could cause this?
package JGame.Actions;
import JGame.GameObject.GameObject;
import javax.swing.AbstractAction;
public class MoveAction extends Action implements Runnable{
protected GameObject obj;
protected int endX = 0, endY = 0;
protected int moveAmount = 0;
protected Thread thread;
public void moveToY(GameObject obj, int y, int amount, AbstractAction complete){
this.obj = obj;
this.endY = y;
this.moveAmount = amount;
this.complete = complete;
thread = new Thread(this);
thread.start();
}
public void run(){
try{
boolean run = true;
while(run){
int objY = obj.getY();
if(objY > this.endY){
obj.setY(obj.getY() - 1);
}else if(objY < this.endY){
obj.setY(obj.getY() + 1);
}else{
run = false;
this.actionComplete();
}
thread.sleep(moveAmount);
}
}catch(Exception e){
}
}
}
Action Complete:
package JGame.Actions;
import javax.swing.AbstractAction;
public class Action {
protected boolean actionComplete = false;
protected AbstractAction complete;
public void actionComplete(){
complete.actionPerformed(null);
}
}
In my code I call moveToY it is a very simple call but sometime the Bullets move at different speeds (wrong), and others they move at the same speed (right). I don't know if it would help to mention that as the bullets move sometimes they slow down for a second or two then speed back up to the correct speed.
Edit: Main Thread
The following is my main thread with the paintComponent
#Override
public void run(){
try{
while(true){
// Check for key press events
Iterator actions = KeyboardMap.map.entrySet().iterator();
while(actions.hasNext()){
Map.Entry ap = (Map.Entry)actions.next();
Mapping mp = (Mapping)ap.getValue();
if(mp.pressed){
mp.run();
}
}
// Check for click mouse events
Iterator actions2 = MouseMap.map.entrySet().iterator();
while(actions2.hasNext()){
Map.Entry ap = (Map.Entry)actions2.next();
Mapping mp = (Mapping)ap.getValue();
if(mp.pressed){
mp.run();
}
}
for(GameObject go : gameObjects){
if(!go.getLeaveScreen()){
int goWidth = go.getWidth();
int goHeight = go.getHeight();
int goX = go.getX();
int goY = go.getY();
int gameWidth = Game.width;
int gameHeight = Game.height;
if(goX + goWidth >= gameWidth){
go.setX(gameWidth - goWidth);
}
if(goX <= 0){
go.setX(0);
}
if(goY + goHeight >= gameHeight){
go.setY(gameHeight - goHeight);
}
if(goY <= 0){
go.setY(0);
}
}
}
this.repaint();
Thread.sleep(roomSpeed);
}
}catch(Exception e){
}
}
public void paintComponent(Graphics g){
try{
g.drawImage(bg, 0, 0, this);
for(int i = 0; i < gameObjects.size(); i++){
GameObject go = gameObjects.get(i);
g.drawImage(go.getSprite(), go.getX(), go.getY(), this);
}
}catch(Exception e){
}
}

Well, I guess you have a large number of concurrent threads running (one by moving bullet), and you expect each thread to wake up after exactly moveAmount milliseconds. You can't have such a guarantee, because the thread scheduler allows each thread to run for some time one at a time, and you might thus have glitches.
Another problem is that you seem to execute modification on Swing components out of the event dispatch thread, which is clearly forbidden by Swing's threading policy.

The most important thing to change in your code is don't model time with Thread.sleep. Use a Swing Timer, which you'll schedule to execute every moveAmount milliseconds and, as a bonus, the code is executed on the Event Dispatch Thread with no effort on your part.

Inform yourself about the usage of multiple threads and how the processing structure of a game is made correctly.
The most important info for your case: You should only use ONE thread to process/move all your bullets and then render them.